Photolithography is a common process used in the fabrication of integrated circuits. During a photolithography process, a process solution, such as a photoresist material, is applied on a semiconductor wafer and is exposed with a predefined pattern to be transferred to the wafer. The characteristics and properties of the process solution may directly affect the quality of the photolithography patterning process and the performance of the thus-formed integrated circuits. Therefore, the quality control of the process solution is essential in the fabrication of integrated circuits.
It is complicated to prepare samples for inspecting the process solution. The sample preparation process of the process solution normally takes a long preparation time, which makes it impossible to inspect a particle or an impurity in the process solution at early stages of the photolithography. In addition, as the process solution has a particle or an impurity in a size less than 10 nm, detection of increasingly smaller defects becomes even more critical and difficult. Accordingly, improvements in the tool and method for inspecting a process solution continue to be needed.